In order to effect the complete precipitation of the aluminum oxide from the solution which was poured from the iron, ammonium hydrate is added, and the solution boiled for some time, and then the aluminum oxide is determined in the usual manner. When the quantity of aluminum is less than that of iron, this method may be relied upon to give exact results. With the reverse (_i. e._, an excess of iron) the precipitate of aluminum oxide must be dissolved in oxalic acid (without the interruption of the current), and the electrolysis continued.--_Berichte der Deutschen Chemischen Gesellschaft_, 14, 1662. * * * * * THE CULTIVATION OF PYRETHRUM AND MANUFACTURE OF THE POWDER. In accordance with an announcement in the March number of the _Naturalist_, the editor of this department has sent out the seed of two species of pyrethrum, viz. _P. roseum_ and _P. cinerarioefolium_, to a large number of correspondents in different parts of North America. Every mail brings us some inquiries for further particulars and directions to guide in the cultivation of the plant and preparation of the powder. We have concluded, therefore, that such information as is obtainable on these heads will prove of public interest, and we shall ask Professor Bessey's pardon for trenching somewhat on his domain. There are very few data at hand concerning the discovery of the insecticide properties of pyrethrum. The powder has been in use for many years in Asiatic countries south of the Caucasus mountains. It was sold at a high price by the inhabitants, who successfully kept its nature a secret until the beginning of this century, when an Armenian merchant, Mr. Jumtikoff, learned that the powder was obtained from the dried and pulverized flower-heads of certain species of pyrethrum growing abundantly in the mountain region of what is now known as the Russian province of Transcaucasia. The son of Mr. Jumtikoff began the manufacture of the article on a large scale in 1828, after which year the pyrethrum industry steadily grew, until to-day the export of the dried flower-heads represents an important item in the revenue of those countries. Still less seems to be known of the discovery and history of the Dalmatian species of pyrethrum (_P. cinerarioefolum_), but it is probable that its history is very similar to that of the Asiatic species. At the present time the pyrethrum flowers are considered by far the most valuable product of the soil of Dalmatia. There is also very little information published regarding either the mode of growth or the cultivation of pyrethrum plants in their native home. As to the Caucasian species we have reasons to believe that they are not cultivated, at least not at the present time, statements to the contrary notwithstanding.[1] [Footnote 1: Report Comm. of Patents, 1857, Agriculture, p. 130.]